The present invention relates to a device for supporting a spool in a paper or board making machine.
With respect to the prior art related to the present invention, reference can be made to the applicant""s FI Patent Application 942451, in which a method and a device in winding of a web are described. The device that carries out this prior-art method has been fitted to be used when a web is wound onto a spool on support of a support roll while the web is passed through a nip formed between the support roll and the roll that is being produced, which spool is at least partly supported by means of a support device fitted in the centre of the spool, which device comprises a unit for supporting the spool and for loading the roll. In this prior-art solution the unit has been fitted as a combined loading/supporting and surface-drive member, and the device comprises means for shifting the unit substantially in a plane passing through the axes of the support roll and of the roll that is being produced as a linear movement and substantially along a curved path in the direction of the circumference of the roll.
With respect to the prior art related to the present invention, reference can also be made to the published EP patent application 292 451, which discloses a belt support unit including belt rolls, around which a carrier belt is fitted. The support unit supports the roll being formed from below at least in the final stages of reeling by extending a belt zone and, at the same time, by adjusting the tension of the carrier belt so that the linear loads in various supporting nips of the roll being produced remain within suitable limit values. According to the publication, the extending of the belt zone and the adjusting of the tension of the carrier belt are accomplished by means of one power cylinder fitted between the belt rolls, and further the support assembly for the belt rolls is accomplished by means of a rhomboid actuated by a second power cylinder.
With respect to the prior art related to the present invention, reference can also be made to the published DE Patent Application 3737503, in which a rigid rider roll unit connected with a reel slitter machine is described. In this prior-art arrangement, bending of the spool at the beginning of winding cannot be prevented, and therefore bending of the spool may cause problems of winding.
With respect to the prior art, reference is also made to the DE Patent 391852, in which a device is described for winding of a material web, in connection with which device, when the web tension bends the spool, the spool is kept straight by pushing by means of a cylinder, which also moves the rider roll head. By means of this arrangement, it is also possible to bend the spool in the opposite direction in order to produce an effect of spreading the web. It is a drawback in this prior-art arrangement that the rolls are stationary in relation to one another, in which case a belt that would improve the friction and distribute the load more evenly cannot be fitted around said rolls, because the belt cannot be tensioned. By means of a belt, the friction coefficient between the roll and the rider rolls can be increased to a considerable extent, and the force applied by the rider roll to the roll in the radial direction of the roll can be distributed more evenly over a wider area. These factors have a great importance for the quality of the roll to be wound, and by means of a belt it is possible to widen the range of application of various winding parameters considerably, in which connection it is better possible to meet the requirements that are imposed by different paper grades on winding that produces good rolls.
The bending of the spool at the beginning of winding arises from a tensile strain present in the web in the longitudinal direction of the web, which strain has the effect that the spool is bent into curve form between its ends and is, thus, not fitted as straight in relation to the cylinder, in which case the winding nip also becomes curved and, thus, problems of winding arise.
An object of the present invention is further development of the solution described in the applicant""s FI Patent Application 942451 mentioned above so that the spool cannot be bent at the beginning., of winding, in which case the spool cannot cause problems in the winding either.
It is a further object to provide a rider roll construction in which it is possible to provide the rider rolls with a drive in order to load the face of the roll in the direction of its circumference. In this way it is, among other things, possible to regulate the tightness of winding.
It is a particular object of the invention to provide a rider roll construction in which an endless belt/belts can be fitted around at least two rider rolls, whereat the tension of these belts can be regulated by varying, the distance between the rolls, and which rider roll construction is capable of transferring forces to the spool and/or roll both in the direction of their radius and in the direction of their circumference.
The arrangement in accordance with the invention consists of a rider roll unit, which supports the spool during winding and, at the same time, prevents bending of the spool during winding. The rider roll unit comprises rolls, around which a belt runs. The rolls in the rider roll unit have been coupled together by means of coupling members so that movements of the rolls in relation to one another are geometrically positively controlled. In a preferred embodiment in accordance with the invention, the relative movements of the rolls take place so that a geometrically controlled, symmetric movement is produced in relation to the central axis of the rider roll unit. Then, the winding gap formed between the rolls of the rider roll unit remains stationary, in which connection the spool remains straight at the beginning of winding.
The arrangement in accordance with the invention is suitable for use in particular in connection with wide rolls, in which, thus, long spools are used, which are highly susceptible of bending. The arrangement in accordance with the invention can be provided with a drive motor, in which case, by means of the arrangement in accordance with the invention, the rolls can be loaded in the direction of the circumference, by which means it is possible to affect the quality of the rolls that are being produced to a great extent.